This invention relates to side channel compressors in general and more particularly to such compressors in which the output characteristic can be changed.
Side channel compressors in which the blades arranged on a rotor have a bevel on the back side of the blades at their lateral edges are generally known. As is further known, the power required in side channel compressors increases if the amount of throttling is increased, and reaches its maximum if the side channel compressor is throttled completely. There are various applications for side channel compressors, in which the latter are also temporarily throttled completely between the normal pumping operation. Since the side channel compressor consumes the most power just when no pumping is necessary, various solutions have already become known to reduce this power in case of complete throttling. One possibility is to connect a pressure limiting valve to the side channel compressor. This, however, requires additional technical means and is expensive.
From the German Offenlegungsschrift No. 1,945,979, FIG. 5, it is known to provide a bevel on the front side of the blade in addition to a bevel on the back side of the blade, to reduce the power of a side channel compressor when it is completely throttled. Another possibility for reducing the power in the completely throttled state is seen in providing sharp deflections in the side channel and at the blade bases. Such mechanical design in a side channel compressor must be taken into consideration from the start in the manufacture of the side channel compressor. This means that such side channel compressors must be designed and manufactured specially for the applications described.
From the German Auslegeschrift No. 1,528,822, FIGS. 3 and 4, a side channel compressor is further known, in which guide ribs are arranged for reducing the power required with increased throttling. Such guide ribs must likewise be provided right from the start, so that this known side channel compressor is specifically designed for such applications where throttling takes place temporarily.
In many applications, however, no throttling of the side channel compressor takes place during operation, so that power limitation in general is not necessary. Since the known measures for limiting power result in a certain amount of efficiency reduction, general employment of side channel compressors designed in this manner is not desirable. So as to always offer optimum efficiency for operation of the side channel compressor with full throttling, as well as for operation of the side channel compressor without throttling, the manufacturer of side channel compressors must practically have two difference types of side channel compressors in his line.